Three phase non-segregated disconnect switches find application in generator compartments for supplying electricity to a power grid. These switches must be capable of withstanding short circuit tests in the order of 80 kA.
One type of disconnect switch used in the three phase non-segregated application comprises a pair of spaced apart elongated blade members which span the distance between first and second electrical terminals of the switch. Typically these spaced apart blades include a spacer between the blades. One end of the blades is pivotally attached to one of the terminals and the other end of the blades has inside edges of the blades making wiping contact with the second electrical terminal. In this switch, as many as three bolts pass through the blades, and springs and nuts are mounted on these bolts so as to control spring loaded compression of the blades with the second electrical terminal. While this spring switch configuration provides a reliable switch for making and breaking the connection at the second electrical terminal, the spring switch does not respond well to 80 kA short circuits in the three phase non-segregated application. During a short circuit, the three phases of the spring switch blades are attracted to each other causing the blades of adjacent phases to be attracted towards each other resulting in at least one of the blades being pulled from the second electrical terminal. This results in arcing and welding of this blade to the second terminal.
Another known construction for a three phase non-segregated disconnect switch is a bolted switch. The bolted switch typically has double switch blades for each phase that carries a bolt that is received within a groove of the second electrical terminal. While the bolted switch is able to withstand the 80 kA short circuit condition, this switch is relatively expensive to manufacture and tends not to be as reliable over time in making and breaking the connection with the second electrical terminal.